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Is there any concerns about using a Tekmar 260 on a non-draft induced(non-condensing) water boiler with cast iron radiators. There is no DHW. I'm worried about mild days and the boiler condensing. If so, whats your recommendations for correcting.

With a non-condensing boiler, you can only achieve a "Partial-Reset". No reset temp below the 140F mark.

I like to apply a permanent mix demand to terminals 1&2. When the outdoor temp drops below the WWSD, the P1 circ will engage and start distributing heat. You will also notice that I wire the thermostat in series with the boiler demand on terminals 11 & 12 so that the boiler will only fire when the stat calls for heat. You get boiler protection, constant flow of a partial reset temp, and overheating the rads will be a thing of the past when you tweak the reset curve.

Terminals 3&4 are for your aquastat leads for your indirect. These are typically powered by 24V(ac). Additionally, terminals 9&10 are for switching power to your indirect zone pump at 120V or you can switch 24V if you are using a zone-valve. (Edit: With a P1 Boiler Pump and P2 Indirect pump, you can toggle a dip-switch for DHW priority.)

Tekmar's website has excellent resources with their A260 (applications brochure) which is available to download.

Is there a piping arrangement that will give you full reset with a non condensing boiler that you are using? Primary secondary and thermostatic valve possibly. I want to get the most I can from reset. Thanks.

With atmospheric boilers, the minimum inlet temperature is 140F. Period. You can reset a temperature to this temp and higher and that gives you a "partial-reset". To give a full reset temp, it would have to go below the 140F temperature.

Can this be done? Yes, if you want to prematurely kill your boiler from sustained flue gas condensation. It will eat out the vent pipe and drip condensate on the CI sections until they give out or crack due to thermal shock.

Spend the money on a modcon if you want full-reset. Reset and modulation alone will pay for the cost difference.

Other options exist with full-reset temperatures and atmospheric boilers. You should consider a variable-speed injection-mixing control. If a modcon is not in the budget, VSIM is an excellent "next best" thing.

The afore mentioned tekmar site has plenty of info and you might consider a Tekmar (Edit:356),361, 362, or 363 based on your needs.

The first drawing was only for space heating and constant flow. Maintaining that and adding the indirect on priority really changes the landscape of that drawing and it would have to be modified quite a bit.

It can be done. Isolation with relays will be the key.

You need a Tekmar 004 relay to isolate the P1 circ, a 003 to power 24v to terminals 11&12 so that you can switch demands between a space heat call with the T-stat still in series, and the boiler demand when a DHW call exists. It also needed one more 004 relay to isolate the P2 pump demand which, when closed, establishes a separate boiler demand for the indirect.

You can do it but not with a 260. You can use a motorized mixing valve to do system reset but you will have to run the boiler to 140 to avoid condensation. System and boiler reset is not advisable with a non-condensing boiler. I have a 260 on my Weil WGO and run the boiler min at 135. Installed an indirect with it and cut my consumption 50% with no signs of any issues in the boiler.